The purpose of this study is to investigate the ways in which members of interorganizational collaborations (IOCs) create and maintain the processes and structures of collaborative organizing. This research argues that IOCs are complex organizations that include ongoing communicative processes among individuals who act as collaborative members and constituent representatives. Specifically, this research seeks to explain how individual boundary spanners come to understand collaborative identities that create structures affecting actions and outcomes of the collaboration. Five research questions are posed using social identity theory as a guide to explore the data collected. The communication processes of IOC boundary spanners was investigated during a 13-month ethnographic field study, which included meeting observations, in-depth interviews, video stimulated recall, and document analysis. Overall, over 90% of the active members in the IOC were interviewed. Data was analyzed using the constant comparative method and organized by research question. Results indicate that boundary spanners in IOC use social identity to help orient and organize the diverse voices present within the collaboration. IOC members invoked group prototypes that created sub-groups within the IOC, thus allowing members with different goals for participation to find ways to justify membership. These prototypes also formed norms for communicating between members and created a collaborative environment that eventually led to organizational collapse. In addition, memberships within the IOC was constantly negotiated between members as the IOC worked towards certain goals. As sub-groups communicatively interacted with each other in the IOC, individuals would become more or less engaged in the collaborative process based on the successes and failures of the sub-group a boundary spanner has joined. Overall, this study helps us better understand how individuals within the IOC experience the collaboration and emphasize the importance of communication in collaborative processes. This study concludes with a discussion of the results and implications of the data for social identity theory, boundary spanner research and IOC research, as well as implications for practice. Limitations and future directions are also discussed.